The present invention relates to a valve timing control apparatus for an internal combustion engine which variably controls timings of opening and closing an engine valve (i.e., an intake valve and an exhaust valve) during an engine operation.
There has been proposed a so-called vane type valve timing control apparatus for an internal combustion engine.
Japanese Patent Application Unexamined Publication No. 2011-85074 discloses such a vane type valve timing control apparatus. The valve timing control apparatus of this conventional art is constructed such that when starting an engine, timings of opening and closing an intake valve is held in an intermediate phase position between a maximum phase-retard position and a maximum phase-advance position by using a lock pin to thereby enhance startability of the engine. In a case where such a lock pin is moved to an unlock position, it is preferable to allow the lock pin to retreat without adverse influence of a hydraulic pressure in a phase-advance hydraulic chamber or a hydraulic pressure in a phase-retard hydraulic chamber. For this reason, in the valve timing control apparatus of the conventional art, a large-diameter flange is integrally formed on an outer periphery of the lock pin and undergoes a hydraulic pressure to thereby move the lock pin to retreat to the unlock position.